Many people wonder why this government makes such a fuss about "Britishness" and citizenship. Lord Goldsmith's review of citizenship offers the cynics and sceptics further ammunition. Among its proposals are "citizenship ceremonies" for all young people and a British national day by 2012. Already, the idea of having young people pledge their allegiance to the Queen has been slammed as a "half-baked idea", "puerile", and "offensive to people who do actually cherish democracy".

Part of the objection to the review's findings has to do with its emulation of American civic rites, namely, the daily pledge of allegiance to the flag taken by schoolchildren. At a time when anti-Americanism lingers, this is an easy way to score political points. Cry that it's too American, and any proposal is likely to be doomed.

Then there's the argument that introducing a British pledge will alienate a significant part of the community. Obvious groups include republicans who reject the monarchy, not to mention religious and maybe even ethnic minorities. The underlying concern here is sensitivity to pluralism and multiculturalism.

The point about Britain not being like America is true at one level. In the context of citizenship, an understanding of British liberty has not been shaped by a language of a republic in the same way as it has been across the Atlantic (the short-lived Cromwellian republic notwithstanding). Liberty, for the last 350 years at least, has been bound up in membership of a constitutional monarchy.

Indeed, the notion of a British "citizen" is relatively new. Being a British "subject" of the crown has been the norm, with citizenship only emerging as a legal concept here in 1948 with the passing of the British Nationality Act.

But perhaps that's all the more reason to get serious about strengthening citizenship. Its importance has never been greater, particularly from a liberal perspective that values pluralism and diversity. The common bond of citizenship is the best option we have to bring people together at a time when they are drifting apart.

Think about the alternatives. It's much harder to insist upon a common cultural identity as the unifying reference point for society. Would any self-respecting liberal wish to do this? Any notion of cultural unity would flirt with ideals of ethnic or racial integrity - with inevitably dangerous consequences.

Put another way, the language of citizenship and a common civic identity is the best friend of any liberal pluralism. If there's something that everyone should share, it's a commitment to fundamental values: the rule of law, representative democracy, freedom of speech and religion, and equality.

The question about pledges and alienation is more complicated. To be sure, it's nonsense to suggest that republicans couldn't make a pledge of allegiance to the Queen (it's about the rules of the game, rather than the symbolic figurehead). And it verges on an empty cultural relativism to say that a pledge would insult certain religious and ethnic minorities who find it difficult to identify with some British public institutions.

At the same time, it's not right that future Britons be asked to pledge allegiance to the Queen, even if she is the head of state. Emphasising loyalty and obligation in this way seems to blur the line between "citizen" and "subject".

This is something which Lord Goldsmith himself appears to acknowledge. While favouring an oath to the Queen, he has conceded that the statement could be a pledge of commitment to the country. This is, for instance, the case in Australia, where naturalising immigrants take the following oath upon becoming a citizen:

"I pledge my loyalty to Australia and its People, whose democratic beliefs I share, whose rights and liberties I respect, and whose laws I will uphold and obey."

The Goldsmith review should rightly provoke a robust debate about the meaning of citizenship in Britain. But its critics and opponents should beware of falling into the trap of believing that any attempt to strengthen understandings of citizenship are simply daft. A complacent or laissez-faire approach to identity can't ever be enough. The risk of any such approach, from a liberal viewpoint, is clear: it can cede the moral vocabulary of Britishness and patriotism to elements wholly undesirable. Where liberals don't stand with an account of citizenship of their own, solidarity can quickly become swallowed up into the kind of chauvinistic, cultural nationalism that everyone should fear.